Lithium ion battery active material dissolution kinetics in Fe(II)/Fe(III) catalyzed Cu-H₂SO₄ leaching system

In mechanical recycling and separation of waste lithium-ion batteries (LIBs), Cu from electrode materials and Fe from battery casings may partially end up into the fine black mass fraction, rich in oxides such as LiCoO₂. Herein the kinetics of LiCoO₂-H₂SO₄-Fe-Cu- system was investigated by leaching studies in a 500 cm³ glass reactor at T = 30 °C, with 2 M H₂SO₄ under N₂(g) purging (0.5 dm³/min). Design of experiments (DOE) was utilized as a supporting tool in investigation of the effect of copper (Cu/2LiCoO₂ = 0.5–1.5 mol/mol,) and iron (Fe/LiCoO₂ = 0.01–0.11 mol/mol) to the measured LiCoO₂ dissolution rate constants at initial phase of leaching (0–30 min) and at final phase of leaching (30–120 min). Analysis of variance showed that the kinetic rate constant models are statistically significant (p = 0.002 and p < 0.000, respectively), furthermore, the models describe real effects (coefficient of determination, R² = 0.920 for <30 min model and R² = 0.9895 for >30 min model). The results suggest that Cu is able to relinquish electrons to ferric ions, and the resulting ferrous ions mediate the transfer of electrons enabling reduction of LiCoO₂. A sufficient Co extraction (>95%) was achieved with solution containing dissolved iron (1.06 g/L), along with 2.167 g of metallic Cu per 6.68 g of LiCoO₂ (1/1 mol ratio)_. It was calculated that the copper present in typical spent LIB cells is enough to satisfy this requirement. This decreases the chemical consumption as there is no need for external reductant.